The transmission of power by means of a transmission system of the kind summarized above may take place by either one of two pathways. The first power path runs via the torque converter which acts at the same time as starting or drive-away coupling. In it, the power is transmitted not via the V-belt transmission, but from the input shaft via the torque converter direct to the secondary shaft of the V-belt transmission, while the primary shaft transmits no power.
The second power path runs via the V-belt transmission. Here, the input shaft drives the primary shaft directly, the torque converter being cut out.
Such a transmission is known from the British Patent application No. 2,025,545, which describes a transmission system whose input shaft, torque converter and primary shaft of the V-belt transmission have been mounted coaxially. In this known system, the input shaft can be held in a fixed position relative to the primary shaft by means of a mechanical coupling, so that the input shaft and the primary shaft rotate as one, giving rise to the aforesaid second power path.
In the transmission system according to the said British Pat. No. 2,025,545, the first power path comes about inasmuch as the output shaft of the torque converter mounted coaxially with the primary shaft drives the secondary shaft by means of chain transmission. Because of this chain transmission, the secondary shaft rotates in the same direction as the input shaft (and the torque converter), which is essential in a design of this type. If a gear-wheel transmission were used, an intermediate gear would have to be inserted in order to obtain the right sense of rotation.